Dental handpieces are known in the art for driving a number of dental tools such as prophy cups, abrading devices, polishing attachments and the like. Most often, a dental handpiece includes a rotating shaft within a housing and attached at one end to a drive motor and at the other end to the dental tool. As the motor causes the drive shaft to rotate, the drive shaft operates to cause the dental tool to rotate.
One common method of attaching the dental tool to the drive shaft is to use a threaded and rotatable coupling, wherein the drive shaft actually drives the coupling. The dental tool is threaded to the coupling and rotates therewith. For hygienic reasons, the dental tool is changed between patients and often, between procedures for a single patient. Therefore, efficient securing and removal of the dental tool is important to the overall efficiency of any given dental procedure.
While mating threads between the coupling device and the dental tool have proven to be efficient in securing the dental tool to the drive shaft, it has been found that removal of the tool from the threaded engagement is often difficult. The physical contact between the mating threads causes a friction fit between them which is often greater than whatever force is necessary to rotate the drive shaft. That is, when it is desired to remove the dental tool, the user will often grasp the tool and rotate it in a direction opposite that required to seat the tool. If the frictional forces between the mating threads are greater than that required to rotate the shaft, then the shaft will rotate and the threads will not disengage. This is often further complicated by the fact that the dental tool is often used with various viscous dental materials which can clog any spaces between the dental tool and the handpiece, making it more difficult to remove the dental tool.
It would not be an acceptable solution to make the force required to rotate the drive shaft greater, because the drive motor would then have to use greater force to rotate the drive shaft. This would serve to shorten the life of the motor.
Further, many low speed dental handpieces have both a forward and a reverse powered rotation function. It is possible to simply reverse the rotation of the drive motor to remove a dental tool. Such reversible motors and their associated control mechanisms, greatly inflate both the complexity and the expense of the handpiece.
For hygienic reasons, it would be desirable to differentiate between a plurality of different handpieces. The present invention provides for this need.
A need exists therefore, for a handpiece capable of permitting efficient securing and removal of a dental tool without the need for severely limiting the free rotation of the drive shaft. The handpiece should allow for such removal of the dental tool without the need for expensive and complex reversible motor capabilities. The handpiece should also allow for easy gripping and manipulation by the user.